"Minecraft Properties" tab is not showing up on rig where the tab is supposed to be there
The 'Minecraft Properties' panel is not a panel that appears in Blender by default and will only appear when you have run a script to enable it. You will either need to write your own Python script to create it or obtain an existing 'IK/FK UI' script.

The tutorial maker doesn't seem to have included the script for the panel in the downloads they provide, but they do link to several tutorials in the video description on how to create your own UI such as this one by CG Cookie.